Printing device, flexible reservoir and working container and feed system

ABSTRACT

In a printing device ( 10 ) of the piezoelectric DOD type for printing a substrate ( 12 ) with a printing medium, comprising a print head ( 16 ), which is arranged in such a manner that it can be moved to and fro substantially transversely with respect to the direction in which the substrate to be printed is conveyed, the working container ( 30 ) for degassed printing medium is coupled to a flexible reservoir ( 32 ). This results in increased productivity.

A first aspect of the invention relates to a printing device forprinting a substrate with a printing medium using the “drop-on-demand”principle, comprising a print head, which is arranged in such a mannerthat it can be moved to and fro substantially transversely with respectto the direction in which the substrate to be printed is conveyed andhas at least one spray nozzle with an interacting piezoelectric elementfor generating and releasing a drop of the printing medium on demand,the spray nozzle being in communication with a flexible workingcontainer, which is arranged at a fixed position, for degassed printingmedium at a working height with respect to the spray nozzle whichworking height lies within a predetermined height range, in order tokeep the pressure of the printing medium in the print head within apredetermined pressure range.

A printing device of this type is known in the art, and is also referredto as a “piezo-DOD inkjet printer”. A device of this type generallycomprises a print head, which is arranged on a carriage which can moveto and fro transversely with respect to the direction of movement of thesubstrate which is to be printed. The print head comprises at least onespray nozzle, generally a number, for example 8 or 16, for each colour,this nozzle being in communication with a flexible working container viaa feed passage. Furthermore, the print head for each spray nozzlecomprises a piezoelectric element for generating ink drops. A shockwavecan be generated electrically in the print head by means of thepiezoelectric element, with the result that each time each shockwaveforms a drop from the printing medium. A drop of this type is onlyformed if it is required in order to print the substrate. This principlehas been given the name drop-on-demand. In addition to “piezo-DOD”,“thermal DOD” is also known, in which heating elements are used insteadof a piezoelectric element to form drops.

It is generally recognized in the art that degassed printing medium isrequired for piezo-DOD. If printing medium which has not been degassed(for conventional types of ink the equilibrium concentration of oxygenis approx. 8 mg of O₂/l at atmospheric pressure) is used, at high firingfrequencies the gas accumulates in the print head, where the accumulatedgas attenuates the shockwaves which bring about the formation of drops.The result of this is that after a certain time has elapsed, fewer dropsare formed, or even no more drops will be formed, and the inkjet printerstarts to malfunction or even stops altogether. With printing mediumwhich has not been degassed, this phenomenon means that it is necessaryeither to use lower firing frequencies or to periodically interruptprinting operation in order to remove the accumulated gas, generally bypurging. Both solutions reduce the productivity of the printing device.If degassed ink is used, this phenomenon, and the associated adverseeffects, do not occur. For example, degassed printing medium has anoxygen concentration of approximately 1 mg/l. If degassed printingmedium is in contact with air for approximately one day, the oxygenconcentration returns to the abovementioned equilibrium value.Therefore, contact with air has to be avoided, although brief contact isacceptable.

The degassing of the printing medium may be carried out on line duringprinting, for example just before the printing medium is supplied to theprint head or in the print head itself. The latter option is used inparticular in relatively large industrial printing devices. Anotherpossibility is to use printing medium which has already been degassed, asolution which is adopted in particular for relatively small standardprinting devices. This imposes higher demands on the packaging, inparticular with regard to its gas and/or air permeability. Examples ofpackaging of this nature are described in European patent applications857 573 and 1 013 449.

In a type of piezo-DOD printing device as described above, the workingcontainer, which is flexible (not dimensionally stable) with a view toallowing it to empty out without the admission of air, is arranged at afixed position and connected to the print head by means of a flexibleline of sufficient length, since allowing the working pouch to move withthe print head, for example on the carriage, can lead to undesirablefluctuations in the pressure of the printing medium in the print head,and therefore to a non-uniform print quality. The known workingcontainer has a relatively small volume (of the order of magnitude of afew hundred millilitres), since the pressure in the print head isrelated to the pressure exerted by the printing medium (volume andworking height with respect to the print head), and consequentlyfrequent replacement by operating staff is required. The printing devicehas to be stopped for this purpose.

Furthermore printing devices are known in the art, which are providedwith feed systems, mostly controlled by valves, for feeding a printingmedium from a reservoir to a working container. Examples thereof areknown from e.g. JP-A-11105299, EP-A-0 927 638 and JP-A-2003118134. Thecomplexity, costs and susceptibility to disturbances of the printingdevice are increased by such systems.

It is an object of the present invention to provide a piezo-DOD printingdevice which can print for a long time. A further object of theinvention is to provide a device of this type in which, duringoperation, if necessary, it is possible to top up or replace the supplyof printing medium. Yet a further object is to maintain the degassedstate of the printing medium. Yet another object is to provide apiezo-DOD printing device which comprises a relatively simple,insensitive to disturbances, and inexpensive feed system for printingmedium in order to allow continuous printing of a substrate with theprinting medium.

This object is achieved, in a printing device of the type described inthe preamble, by virtue of the fact that the working container is incommunication with a releasable, flexible reservoir for degassedprinting medium. According to the invention, the total stock of printingmedium is formed by the content of the relatively small workingcontainer and the content of a relatively large reservoir, which mayhave a volume of, for example, a few litres. The working container andthe reservoir form communicating vessels during normal operation due tothe open connection between them. During printing, printing medium whichis required flows out of the working container towards the print headfor use in the printing process. The working container, on account ofthe communication with the reservoir as communicating vessels, isautomatically topped up from the reservoir, with the pressure of theprinting medium in the print head being kept within a defined pressurerange as a result of the pressure exerted by the stock of printingmedium. As a result of the open connection the liquid pressure at acertain height in the reservoir is equal to the liquid pressure at thesame level in the working container. This does not apply, if between therespective containers valves, shut-of means and closing devices arepresent, which are controlled, and/or consecutively and repeatedlyclosed and opened during operation. In the printing device according tothe invention an equilibrium is established between the hydrostaticpressures and height levels of the printing medium in the containers bymeans of free liquid exchange due to the open connection duringoperation. Since the reservoir and the working container are arranged ata fixed position, when the reservoir is empty the latter can beuncoupled. There is no need to interrupt operation of the printingdevice to do this, since the quantity of printing medium which ispresent in the working container functions as a buffer which issufficient to cover the time required for replacement. Therefore, thereservoir can be changed during operation (“on the fly”). During thisbrief exchange of the reservoir, the open connection between thereservoir and the working container is temporarily interrupted, forexample by means of a open/closed valve.

In the printing device according to the invention both the workingcontainer and reservoir are flexible and suitable for degassed printingmedium. A dimensionally stable container does not allow to maintain theprinting medium in a degassed state during operation of the printingdevice, because during operation in that situation either anunderpressure is generated in the container that causes the printingprocess to stop because printing medium is no longer delivered, eitherair is sucked in from the environment into the container, which aircontacts the printing medium thereby removing its degassed state.

In other words, during operation of the device according to theinvention the working container is continuously in open connection withthe reservoir, except during exchanging or replacing the reservoir.During such an exchange, the entry of air into the working container isprevented.

To promote this emptying of the printing medium, the reservoir isadvantageously positioned at a height difference, generally a relativelysmall height difference, above the working container. In this preferredembodiment, the bottom of the reservoir is located at a slightly higherlevel than the bottom of the working container, so that during operationthe reservoir empties out slightly earlier than the working container.The working height of the working container and the height differencebetween the reservoir and the working container are determined by thepressure in the print head, which has to be sufficient to form andrelease drops in the event of the piezoelectric element being activatedand to keep the feed passage of the print head full. If the reservoir ispositioned at an excessively high position, the pressure exerted in theprint head by the printing medium will be so great that printing mediumwill leak out of the spray nozzle. If the reservoir is positioned at anexcessively low position, the meniscus of the printing medium will breakin the print head during the suction movement of the piezoelectricelement. In the event of an extremely low pressure in the print head (asa result of a very low position of the working container), there is arisk of air being sucked in from the environment through the spraynozzle. In the printing device according to the invention, no additionalmeans, such as pumps and the like, are used to feed the printing mediumto the print head from the working container or to feed printing mediumfrom the reservoir to the working container.

Since the reservoir has a relatively large volume, the decrease in thequantity of printing medium therein as a result of a drop in levelduring printing can have a relatively extensive influence on thepressure in the print head. As an additional measure to the heightdifference between the flexible reservoir and the working container andprint head, the reservoir advantageously has a low shape, i.e. a smallheight dimension, so that the drop in the level of the printing mediumin the reservoir which occurs during printing does not have anyunacceptable effect on the pressure in the print head. A narrowreservoir is preferred, with a view to materials costs. In addition,this allows a plurality of reservoirs, one for each colour, to bepositioned laterally next to one another over a relatively short length.For a given delivering volume, a preferred reservoir is a low, narrowand long pouch.

To promote the outflow of the printing medium when the quantity ofprinting medium in the reservoir decreases during operation, inparticular when the reservoir is virtually empty, a preferred embodimentof the printing device according to the invention is provided withdisplacement means for moving the reservoir upwards with respect to theworking container, in particular that end of the reservoir which isremote from the working container. In this way, the level of theprinting medium in the reservoir with respect to the working containercan be monitored and controlled within predetermined permissible limits.

According to a further embodiment, the displacement means comprisesupport means, which can be tilted in the direction of the workingcontainer, for supporting the reservoir. Tilting causes the outletopening of the reservoir to remain at approximately the originalposition with respect to the working container, while the drop in levelof the printing medium is compensated for by tilting. The support meansadvantageously comprise a support plate which can rotate about arotation point located in the vicinity of the end which faces theworking container, and at the opposite end is connected tocounter-pressure means, such as a counter-pressure spring, and which inthe horizontal position bears against supporting means, for example a(fixed) support point below the support plate, or a (fixed) supportpoint located above it in the vicinity of that end of the support platewhich faces towards the working container. Since the mass of the supportmeans and the reservoir with contents positioned thereon graduallydecreases during operation, after a limit value which is defined by thecounter-pressure means has been exceeded, the support means aregradually tilted about the rotation point by the counter-pressure means.

This displacement is advantageous in particular if the reservoir isvirtually empty, so that even the final residues can flow out of thereservoir. Prior to this displacement, the reservoir is lying in asubstantially horizontal position against the supporting means.

Advantageously signalling means for remote detection of tilting of thesupport plate are provided. In addition to visual detection of thetilting by the operating staff, the signalling means can, for example,produce a light or sound signal in order to notify the operating staff.This is advantageous in particular if one operator is responsible for aplurality of printing devices. The moment of tilting can be adjusted byadapting the various components to one another in such a way that theremainder of the reservoir then flows into the working container withina relatively short time. In other words, the residual quantity ofprinting medium in the reservoir, when the tilting commences, can beadjusted by means of the counter-pressure means. This tilting momentthen indicates that replacement of the reservoir is required. Thesignalling means can be connected to a detection switch which isenergized in the event of tilting.

The modification of a conventional piezo-DOD printing device inaccordance with the invention allows the uninterrupted operating time tobe considerably lengthened, for example to 10 hours compared to anoperating time of 2-3 hours for a printing device according to the priorart, while the pressure in the print head can be maintained withinaccurate limits, so that there are no changes in the print quality andink yield during the operating period. Existing piezo-DOD devices caneasily be adapted in accordance with the invention (retrofitting). It ismerely necessary to adapt the working container cartridge by theprovision of an additional connection or coupling to the reservoir. Theelectronics and control technology of the printing device remainunaffected.

The flexible reservoir is advantageously made from a metalized plasticfilm which is gas-impervious. It is more preferable for the material ofthe flexible reservoir to have a sandwich structure. An aluminiumbarrier layer which is provided with a polyethylene or polypropylenefilm on both sides is one suitable example. The thickness of thereservoir is such that the reservoir is sufficiently flexible to adaptto the change in volume which occurs during printing, in order tomaintain the degassed state of the printing medium without any ingressof air. According to a further preferred embodiment, the heightdimension (thickness) of the reservoir in the completely filled state issmaller than the height dimension of the working container. In asituation of this nature, if the reservoir is positioned at a workingheight which is slightly above the bottom of the working container, thepressure in the print head cannot depart from the design limits of theprinting device.

The reservoir advantageously comprises a front surface and a rearsurface, which are connected to one another along the periphery, with anoutlet opening, which is in fluid communication with connecting meansfor coupling to the working container, being provided in a peripheralpart. It is advantageous to use gas-impervious couplings, for examplemade from PVdF or plastic which is itself insufficiently gas-imperviousbut has been provided with a barrier layer. For rapid coupling, theconnecting means of the reservoir and of the working container areadvantageously quick-fit couplings, comprising complementary parts,which are known per se.

To enable the printing medium to flow out correctly, the said peripheralpart is preferably shaped in such a manner that the inner wall of thereservoir has a gradual transition in the direction of the outletopening. One possibility in this respect, in the case of an elongate andrectangular reservoir, is for the corners of a rectangular front andrear surface to be connected to one another along a curved line at thesaid peripheral part, generally the top side. As has already beendiscussed above, in the filled state the flexible reservoir isadvantageously a long, low and narrow pouch. According to a particularlypreferred embodiment, the ratio of the length of a front surface of thereservoir to its width is greater than 2.5, more preferably greater than3.

A further aspect of the invention relates to a flexible reservoir,filled with degassed printing medium, in particular obviously intendedfor a printing device according to the invention, which reservoircomprises a front surface and a rear surface made from a gas-impervious,metalized plastic film, which are connected to one another along theperiphery, a closable outlet opening with connecting means for couplingto the working container being provided in a peripheral part. Preferredembodiments of this reservoir are defined in the dependent claims. Toprotect the reservoir during storage and transport and to improve itshandling properties, the flexible reservoir can be packed in aprotective packaging, such as a (cardboard) box, in which case only theconnecting means project out of the packaging. The abovementionedsupport means are in this case preferably designed in such a manner thatthe reservoir with protective packaging is placed directly into or ontothem.

Yet another aspect of the invention relates to a flexible workingcontainer for degassed printing medium, in particular obviously intendedfor use for a printing device according to the invention, comprising aflexible container made from a gas-impervious, metalized plastic film, afirst peripheral part of which is provided with an outlet opening withconnecting means for coupling to a feed leading to a print head, and asecond peripheral part of which is provided with an inlet opening withconnecting means for coupling to a reservoir. When the working containeraccording to the invention is in use, printing medium flows through it(semi-)continuously, so that no “old” ink or other printing mediumremains behind in it. In this way, the working stock is continuouslyrefreshed.

Yet a further aspect of the invention relates to a feed system forfeeding a printing medium to a printing device, in particular obviouslyintended for a printing device according to the invention, whichcomprises a flexible reservoir according to the invention which isoperatively connected to a working container according to the invention.

The present invention is illustrated herein below on the basis of theappended drawing, in which:

FIG. 1 diagrammatically depicts an embodiment of a printing deviceaccording to the invention;

FIG. 2 diagrammatically depicts an embodiment of a feed system accordingto the invention; and

FIG. 3 shows an embodiment of a flexible reservoir for degassed printingmedium according to the invention.

In FIG. 1, a piezo-DOD printing device according to the invention isdenoted overall by reference numeral 10. The printing device 10 is usedfor the continuous printing of a substrate 12 in web form which isconveyed through the printing device with, for example, a repeatingpattern of printed images 14. The conveying direction of the substrateis denoted by a single arrow. For the sake of simplicity, the means forconveying the substrate, such as one or more driven rollers, are notshown. The printing device 10 comprises a print head 16, which isarranged on a carriage (not shown). The carriage can move to and fro ina transverse direction (as indicated by a double arrow) with respect tothe conveying direction of the substrate, along rails 18 via a suitabledrive (not shown), such as a toothed belt drive. One or more spraynozzles 20 are provided for each colour, such as black, magenta, yellowand cyan, in the print head 16, which nozzles are connected, via a feedpassage 22 in the print head 16, to a flexible feed line 24 (only one ofwhich is shown). A piezoelectric element 26 is provided in the vicinityof that end of the feed passage 22 which lies at the spray nozzle 20.The element 26 is energized on demand in order to generate shockwaves inthe printing medium which is present in the feed passage 22 and in thisway to form drops 28. The flexible feed line 24 is in turn incommunication with a working pouch 30 for degassed printing medium, suchas degassed printing ink. This working pouch 30 is arranged at a fixedworking height with respect to the print head 16. A flexible reservoir32 according to the invention is also arranged at a fixed position andis connected to the working pouch 30 via a flexible connection 34.

FIG. 2 diagrammatically depicts an embodiment of a feed system accordingto the invention in more detail. Those components which correspond toFIG. 1 are denoted by the same reference numerals. The working pouch 30with a relatively small volume of, for example, 300 ml is arranged at afixed position and at a predetermined working height with respect to theprint head. This working height lies within a predetermined heightrange, the limits of which are determined by the print head. On the onehand, ink leaks out of the print head if the working pouch is positionedat an excessively high working position with respect to the print head.On the other hand, the meniscus of the printing medium in the print headbreaks during the suction movement of the piezoelectric element if theworking pouch is positioned at an excessively low working height withrespect to the print head. In the event of extremely low pressuresentailed by an extremely low position of the working pouch, the workingpouch may even suck printing medium out of the print head, so that airis sucked into the print head itself. On an exit side 40 of the workingpouch 30, the latter is provided with an outlet opening 42 which isconnected to, for example, a needle connection 44 of the feed passage ofthe print head. On the opposite side 46, the working pouch 30 isconnected to the flexible reservoir 32 via a releasable coupling 34,optionally provided with a open/closed shut-off means 47. The flexiblereservoir 32 is arranged in a box-like body 48 which protects thereservoir 32 from damage, both during storage and transport and duringoperation. The elongate reservoir 32 is supported by a support plate 50which extends in the longitudinal direction of the reservoir 32 and ofwhich the end 52 facing the working pouch 30 is supported on a rotationpoint 54 or connected to a pivot pin. At the other end 56, the supportplate 50 is supported by a counter-pressure spring 58, which isdepressed by the weight of the support plate 50 in conjunction with theflexible reservoir 32, the contents of the latter and the box-likeprotective body 48. Furthermore, in the vicinity of this end, there is aswitch 62 which is energized via a lever 60. In the horizontal position,approximately in the centre, the support plate 50 rests on a supportpoint 51. The rotation point 54, support point 51 and thecounter-pressure spring 58 can be secured to a table 64 of adjustableheight (FIG. 1). To keep the pressure of the printing medium in theprint head within accurately defined limits, the support plate 50 (andtherefore the flexible reservoir with printing medium) is placed at afixed height with respect to the working pouch 30. In an embodiment of aprinting device which is supplied by the Applicant under the trade name“Sapphire”, after this printing device has been modified in accordancewith the invention the underside of the flexible reservoir 32 will lieapprox. 3.5 cm above the underside of the working pouch 30. The shape ofthe reservoir 32 is such that in the completely filled state the topside of the reservoir 32 lies within a margin of 5 cm from the bottom ofthe reservoir 32. The reason for this is that the pressure in the printhead during the emptying of the working pouch 30 and the reservoir 32 isto remain stable within 5 cm water column in this type of printingdevice. For a relatively large stock volume of printing medium in thereservoir 32, the reservoir takes the form of a relatively long, narrowand low pouch, for example with dimensions of 500×150 mm for a fillingvolume of approx. 2 litres. During printing, over the course of time theflexible reservoir 32 will gradually empty out and become lighter, sothat the spring force exerted by the counter-pressure spring 58 will ata given moment be sufficient to lift the support plate 50 out of thehorizontal position and to tilt it about the rotation point 54. Thistilting actuates the switch 62, so that a signal lamp 66 lights up. Oneend 56 of the support plate 50, after the weight of the latter on thecounter-pressure spring 58 has dropped below the counter-force exertedby the counter-pressure spring, will gradually tilt upwards, under theinfluence of the counter-pressure spring 58, about the rotation point 54at the other end of the support plate 50. This promotes completeemptying of the reservoir 32, while the pressure at the print headremains within the required pressure range. The switch 62 detects thatthe quantity of printing medium in the reservoir 32 has almost run outand an alarm via the signal lamp 66 is used to warn operating staff thatthe reservoir 32 needs to be replaced. Since there is still a stock ofprinting medium in the working pouch 30, which functions as a buffer,there is no need to interrupt operation of the printing device itself inorder to carry out this replacement.

FIG. 3 shows an embodiment of a flexible reservoir 32 according to theinvention. The flexible reservoir 32 is made from a metalized plasticfilm which is sufficiently flexible to allow the reservoir to empty outwithout air entering it. If a multilayer film comprising, for example,outer polyethylene layers with a barrier layer of aluminium between themis used, the barrier layer has the function of on the one handpreventing the printing medium from evaporating during storage and atthe same time of preventing the ingress of external air. The reservoir32 comprises a front surface 80 and rear surface, which are connected toone another in a gas-tight manner along the periphery 82. In aperipheral part 84 there is an outlet opening 85 with a connecting means86 which can be closed off, for example by means of a cap (not shown).At this peripheral part 84, the securing of the front surface 80 to therear surface is such that the inner edge 88 of the flexible reservoir 32merges smoothly into the outlet opening 85. As a result, no printingmedium remains behind in the reservoir 32 during printing.

1. Printing device for printing a substrate with a printing medium usingthe “drop-on-demand” principle, comprising a print head, which isarranged in such a manner that it can be moved to and fro substantiallytransversely with respect to the direction in which the substrate to beprinted is conveyed and has at least one spray nozzle with aninteracting piezoelectric element for generating and releasing a drop ofthe printing medium on demand, the spray nozzle being in communicationwith a flexible working container, which is arranged at a fixedposition, for degassed printing medium at a working height with respectto the spray nozzle which working height lies within a predeterminedheight range, in order to keep the pressure of the printing mediumwithin a predetermined pressure range, wherein the working container isin communication with a releasable flexible reservoir for degassedprinting medium.
 2. Printing device according to claim 1, wherein thereservoir is positioned at a height difference above the workingcontainer.
 3. Printing device according to claim 1, wherein the printingdevice is provided with displacement means for moving the reservoirupwards with respect to the working container.
 4. Printing deviceaccording to claim 3, wherein the displacement means comprise supportmeans, which can be tilted towards the working container, for supportingthe reservoir.
 5. Printing device according to claim 4, wherein thesupport means comprise a support plate, which can rotate about arotation point located in the vicinity of the end which faces theworking container, and at the opposite end is connected tocounter-pressure means, and which in the horizontal position bearsagainst supporting means.
 6. Printing device according to claim 5,wherein there are signalling means for remote detection of tilting ofthe support plate.
 7. Printing device according to claim 6, wherein thesignalling means are connected to a switch, which is energized in theevent of the support plate tilting.
 8. Printing device according toclaim 1, wherein the flexible reservoir is made from a metalized plasticfilm which is impervious to gas.
 9. Printing device according to claim1, wherein the reservoir has a height dimension and the workingcontainer has a height dimension, wherein the height dimension of thereservoir, in the completely filled state, is smaller than the heightdimension of the working container.
 10. Printing device according toclaim 1, wherein the reservoir has a front surface and a rear surface,which are connected to one another along the periphery, an outletopening with connecting means for coupling to the working containerbeing provided in a peripheral part.
 11. Printing device according toclaim 10, wherein the peripheral part is shaped in such a manner thatthe inner wall of the reservoir has a gradual transition in thedirection of the outlet opening.
 12. Printing device according to claim10, wherein the front surface of the reservoir has a length and a width,wherein the ratio of the length of the front surface of the reservoir toits width is greater than 2.5.
 13. Flexible reservoir, filled withdegassed printing medium, intended for a printing device according toclaim 1, which reservoir comprises a front surface and a rear surfacemade from a gas-impervious, metalized plastic film, which are connectedto one another along the periphery, a closable outlet opening withconnecting means for coupling to a working container being provided in aperipheral part.
 14. Reservoir according to claim 13, wherein the frontsurface has a length and a width, wherein the ratio of the length of thefront surface of the reservoir to its width is greater than 2.5. 15.Reservoir according to claim 13, characterized wherein the peripheralpart is shaped in such a manner that the inner wall of the reservoir hasa gradual transition in the direction of the outlet opening.
 16. Workingcontainer for degassed ink, intended for use for a printing deviceaccording to claim 1, comprising a flexible container made from ametalized plastic film, a first peripheral part of which is providedwith an outlet opening with connecting means for coupling to a feedleading to a print head, and a second peripheral part of which isprovided with an inlet opening with connecting means for coupling to areservoir.
 17. Feed system for feeding a printing medium to a printingdevice, intended for a printing device according to claim 1, wherein thesystem comprises a flexible reservoir, which is operatively connected toa working container, wherein the reservoir comprises a front surface anda rear surface made from a gas-impervious, metalized plastic film, whichare connected to one another along the periphery, a closable outletopening with connecting means for coupling to the working containerbeing provided in a peripheral part, and the working container comprisesa flexible container made from a metalized plastic film, a firstperipheral part of which is provided with an outlet opening withconnecting means for coupling to a feed leading to a print head, and asecond peripheral part of which is provided with an inlet opening withconnecting means for coupling to the reservoir.